Charles a



(No Model.)

C. A. RANDALL. Telephonie Receiver.

Patented May 3,1881.

Nrren STATES Arent CHARLES A. RANDALL, OF NEY YORK, N. Y.

TELEPHONIC RECEIVER.

SPECIFICATIQN forming part of Letters Patent No. 241,065, dated May 3, 1881, Application filed February 4, 1881. (No model.)

T 0 all whom it may concern Be it known that I, CHARLES A. RANDALL, a citizen ot' the United States, residing` at New York city, New York. have invented new and useful Improvements in Telephonie Receivers, ot' which the following is a specilication.

This invention relates to an articulatin g telephonic receiver for usein connect-ion with a battery-transmitter-that is, a transmitterot that class in which the vibrations ot' a diaphragm or other vibrator cause a variation in a batterycurrent, and also oi' that class in which the vibrations ot' a diaphragm or other vibrator cause an actual make and break of the battery-current which traverses the line and controls the action ofan electro-magnet upon the diaphragm or other vibrator ot' the receiver.

The object oi' my invention is to obviate the production of those inarticulate drumming sounds which are often mingled with the articulate communication delivered by the receiver, and which are usually caused by breaks of the circuit, resulting from speaking too loud in front ot' the transmitter, and thus causing vibrations ot excessive amplitude in its diaphragm or other vibrator, such excess oi' Inovenient separating the contact-points ot' the transmitter too long or irregularly, and thus unduly breaking the circuit and causing abrupt discharge or demagnctization, and recharge or magnetization of the electro-magnet ot' the receiver, these abrupt discharges and recharges resulting in sudden and violent vibrations of the receiver-diaphragm or other vibrator and the production thereby of the objectionable sounds before referred to.

The invention also has in view the construction of an electro-magnet in such a manner that its core will continue to be magnetized to a degree after the cessation oftlow oi' the prime electric current which enlivens it, and'thus abrupt discharge be prevented, and the action of the core extended during a time sufficientfor the re-establishment of the continuity ot lche circuit when it has been broken by the excessive vibration of a transmitterdiaphragm or other vibrator, so thata continuous action of the electro-magnet upon its armature is maintained, and movements caused by it in a receiver-dia phra-gm or vibrator will have an undulatory character, causing air-vibrations producing ar ticulate sounds corresponding to those at the transmitter, instead ot' abrupt and violent v1- brations, which would result from the sudden discharge and recharge of the receiver-magnet.

Another objectot my improvement is to produce an exten sive amplitude ot' vibration in the diaphragm or other vibrator ot' a telephonie receiver, and thus promote distinctuess and volume in the sounds emanating therefrom.

ln the accompanying drawings, Figure l is a section through a telephonie receiver constructed according to my invention, and Fig. 2 is a section ot' a receiver in which the magnet acts directly upon the diaphragm or vi brator.

The letter A indicates a box or case, having in one wall an aperture closed by a diaphragm or sounding-plate, B, which is surrounded by an ear-piece, C, theinner edge ot' which serves to hold the surrounding plate in place.

The letter D designates an electro-magnet constructed according to my invention, and composed ot a soitiron core, E, surrounded directl y by a priant-ry helix, F, of comparatively coarse wire, the terminals ot' which are connected with the screw-posts g and g', respectively, a secondary helix, H, surrounding said helix and formed of finer wire, and au auxiliary coil, l, surrounding the portion of the core projecting beyond the primary coil and having its terminals connected,respectively,vvith those of the secondary helix H, as shown at k k'. An armature, L, secured to a lever, M, pivoted at m, is arranged to face the end of the core E, and the upper end of the leverM is connected by a light rod, N, with the center of the soundin g-'plate or may simpl yimpinge thereon. The auxiliary coil l is wound in proper direction to induce in the core a polarity similar to that caused by the primary helix. The line-Wire is to be connected to one of the screw-posts g or g and the other post connected with the ground.

\Vhen electrical impulses are caused by a transmitter to traverse the line and primary helix F the magnet-core E, in response to these impulses, acts upon the armature L, causing the lever M to vibrate and communicate vibrations having an amplitude much greater than could be produced by the direct action of the magnet uponthe plate, as the extent of movement of the free end of the lever is obviously much greaterthan the distance through which the magnet could electively exercise its attractive power upon a confined diaphragm. By this arrangement I secure the production by the sounding-plate ot' sounds of great volume and distinetness, and relieve the listener of the strain occasioned by the close attention heretofore necessary to catch the words of telephonie receivers. Then the circuit is broken at the transmitter by the cause heretofore referred to, or any other, the core E of the receiver is not instantly demagnetized and suddenly remagnetized when the circuit is re-established, for the instant the current ceases to ilow in the prim ary helix F, an induced current flows over the secondary helix H, and thence over the auxiliary coil I, thus inducing` in the core a continuance ot' its magnetization, which maintains unbroken or only gradually loses its control of the armature L, so that sudden and violent `vibrations of the sounding-plate are prevented, as already explained.

In Fig. 2 the magnet, as described with reference to Fig. l, is shown as arranged to act directly upon the diaphragm or sounding-plate B', and the armature, lever, and connectingrod omitted.

Ihe operation ofthe magnet, as far as is concerned the continuance of action,is the same in the modification as before explained, a metallic diaphragm or vibrator being used.

What I claim is- 1. In a telephonie receiver, the combination, with a sounding-plate or vibrator, of' the electro-magnet D, composed oi' the core, primary and secondary helices, and the auxiliary coil connected with said secondar i helix, substantially as described.

2. In a telephonie receiver, the combination, with the sounding-plate or vibrator, ot' the electro-magnet composed oi' the core, the primary and secondary helices, and the auxiliary coil connected with said secondary helix, and the armature L, the lever carryil'ig said armature and the rod connecting said lever with the diaphragm or vibrator, substantially as described.

In testimony' whereof I have hereunto Set my hand in the presence of two subscribing witnesses.

CHARLES ADAMS RANDALL.

Witnesses:

PHILIP G. RANDALL, (l1-Ins. W. XV. BALL. 

